Measurement of the Slope Parameter $\alpha$ for the $\eta\to 3\pi^0$ decay with the Crystal Ball detector at the Mainz Microtron (MAMI-C)

TL;DR

This study measures the slope parameter alpha for the eta to 3 pi0 decay using the Crystal Ball detector at MAMI-C, providing a precise value that aligns with recent results and investigates the pi0 pi0 invariant mass spectrum for threshold effects.

Contribution

The paper presents a high-precision measurement of the eta to 3 pi0 decay slope parameter alpha using a large dataset and investigates the pi0 pi0 invariant mass spectrum for cusp-like structures.

Findings

Measured alpha = -0.032 ± 0.003, consistent with recent results.

Largest dataset of 3 million events for this decay.

No significant cusp effect observed near the pi+ pi- threshold.

Abstract

The dynamics of the $\eta\to 3\pi^0$ decay have been studied with the Crystal Ball multiphoton spectrometer and the TAPS calorimeter. Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz microtron MAMI-C and tagged by the Glasgow photon spectrometer were used for $\eta$-meson production. The analysis of $3 \times 10^6$ $\gamma p \to \eta p \to 3\pi^0 p \to 6\gamma p$ events yields the value $\alpha=-0.032\pm0.003$ for the $\eta\to 3\pi^0$ slope parameter, which agrees with the majority of recent experimental results and has the smallest uncertainty. The $\pi^0\pi^0$ invariant-mass spectrum was investigated for the occurrence of a cusplike structure in the vicinity of the $\pi^+\pi^-$ threshold. The observed effect is small and does not affect our measured value for the slope parameter.